testsAndMisc/focus_owner/lib/policy.dart

import 'dart:convert';

import 'package:flutter/services.dart' show AssetBundle, rootBundle;

/// Schema version this build understands.
///
/// The asset is generated by `python3 -m python_pkg.focus_policy`, which is the
/// single source of truth. Refusing an unknown version is deliberate: silently
/// accepting a newer schema would mean enforcing a policy this code has
/// misread, and a misread allowlist is an allowlist that blocks the dialer.
const int kSupportedSchemaVersion = 1;

/// Raised when the bundled policy cannot be trusted.
class PolicyFormatException implements Exception {
  const PolicyFormatException(this.message);

  final String message;

  @override
  String toString() => 'PolicyFormatException: $message';
}

/// A nightly window that may wrap midnight (23:00 -> 05:00).
class CurfewWindow {
  const CurfewWindow({required this.startMinutes, required this.endMinutes});

  /// Parses an `{"start": "23:00", "end": "05:00"}` object.
  factory CurfewWindow.fromJson(Map<String, Object?> json) {
    return CurfewWindow(
      startMinutes: _parseHhMm(json['start'], 'curfew.start'),
      endMinutes: _parseHhMm(json['end'], 'curfew.end'),
    );
  }

  /// Minutes since midnight.
  final int startMinutes;
  final int endMinutes;

  /// Whether [minutesSinceMidnight] falls inside the window.
  ///
  /// Wrapping windows are the normal case here, so "inside" means at or after
  /// the start *or* before the end, not both.
  bool contains(int minutesSinceMidnight) {
    if (startMinutes <= endMinutes) {
      return minutesSinceMidnight >= startMinutes &&
          minutesSinceMidnight < endMinutes;
    }
    return minutesSinceMidnight >= startMinutes ||
        minutesSinceMidnight < endMinutes;
  }
}

/// The home anchor. Coordinates are null in a redacted policy.
class HomeLocation {
  const HomeLocation({
    required this.latitude,
    required this.longitude,
    required this.radiusM,
    required this.hysteresisM,
  });

  /// Parses the `home` object.
  factory HomeLocation.fromJson(Map<String, Object?> json) {
    return HomeLocation(
      latitude: (json['latitude'] as num?)?.toDouble(),
      longitude: (json['longitude'] as num?)?.toDouble(),
      radiusM: _requireNum(json['radius_m'], 'home.radius_m'),
      hysteresisM: _requireNum(json['hysteresis_m'], 'home.hysteresis_m'),
    );
  }

  final double? latitude;
  final double? longitude;
  final double radiusM;
  final double hysteresisM;

  /// Whether this policy carries real coordinates.
  ///
  /// The committed asset is redacted, so the location gate cannot run against
  /// it. Enforcement must check this rather than treating a missing coordinate
  /// as (0, 0), which would put "home" in the Atlantic.
  bool get hasCoordinates => latitude != null && longitude != null;
}

/// The device-independent focus policy, as generated from `config.sh`.
class FocusPolicy {
  const FocusPolicy({
    required this.home,
    required this.allowedPackages,
    required this.nightAllowedPackages,
    required this.neverDisablePrefixes,
    required this.workoutUnblockDomains,
    required this.curfew,
    required this.launcherPackage,
  });

  /// Parses a rendered policy document.
  factory FocusPolicy.fromJson(Map<String, Object?> json) {
    final version = json['schema_version'];
    if (version != kSupportedSchemaVersion) {
      throw PolicyFormatException(
        'unsupported schema_version $version '
        '(this build understands $kSupportedSchemaVersion)',
      );
    }
    final home = json['home'];
    if (home is! Map<String, Object?>) {
      throw const PolicyFormatException('missing "home" object');
    }
    final curfew = json['curfew'];
    return FocusPolicy(
      home: HomeLocation.fromJson(home),
      allowedPackages: _stringSet(json['allowed_packages'], 'allowed_packages'),
      nightAllowedPackages:
          _stringSet(json['night_allowed_packages'], 'night_allowed_packages'),
      neverDisablePrefixes: _stringSet(
        json['never_disable_prefixes'],
        'never_disable_prefixes',
      ),
      workoutUnblockDomains: _stringSet(
        json['workout_unblock_domains'],
        'workout_unblock_domains',
      ),
      curfew: curfew == null
          ? null
          : CurfewWindow.fromJson(curfew as Map<String, Object?>),
      launcherPackage: json['launcher_package'] as String?,
    );
  }

  /// Loads the policy bundled with the app.
  static Future<FocusPolicy> load({
    AssetBundle? bundle,
    String assetKey = 'assets/policy.json',
  }) async {
    final raw = await (bundle ?? rootBundle).loadString(assetKey);
    final decoded = jsonDecode(raw);
    if (decoded is! Map<String, Object?>) {
      throw const PolicyFormatException('policy asset is not a JSON object');
    }
    return FocusPolicy.fromJson(decoded);
  }

  final HomeLocation home;
  final Set<String> allowedPackages;
  final Set<String> nightAllowedPackages;
  final Set<String> neverDisablePrefixes;
  final Set<String> workoutUnblockDomains;
  final CurfewWindow? curfew;
  final String? launcherPackage;

  /// Whether a package must never be disabled.
  ///
  /// Prefix-matched on whole labels, so `com.android.providers` covers
  /// `com.android.providers.telephony` but not `com.android.providersomething`.
  bool isProtected(String package) => neverDisablePrefixes.any(
        (prefix) => package == prefix || package.startsWith('$prefix.'),
      );

  /// Whether a package may run under the given conditions.
  bool isAllowed(String package, {bool duringCurfew = false}) {
    if (isProtected(package)) return true;
    return duringCurfew
        ? nightAllowedPackages.contains(package)
        : allowedPackages.contains(package);
  }

  /// Whether the curfew is in force at [minutesSinceMidnight].
  bool isCurfewActive(int minutesSinceMidnight) =>
      curfew?.contains(minutesSinceMidnight) ?? false;

  /// Packages released while a workout is in progress.
  ///
  /// The rooted system expressed this exception as *domains*, because it
  /// enforced through a hosts file. Hiding apps is a coarser instrument: there
  /// is no way to unblock youtube.com without unhiding the YouTube app, so the
  /// exception is expressed as packages here.
  ///
  /// Derived from [workoutUnblockDomains] rather than configured separately,
  /// so that the shell config stays the single source of truth for *intent*
  /// even though the mechanism differs.
  Set<String> get workoutExemptPackages {
    const domainToPackages = <String, List<String>>{
      'youtube.com': [
        'com.google.android.youtube',
        'com.google.android.apps.youtube.music',
      ],
    };
    final packages = <String>{};
    for (final entry in domainToPackages.entries) {
      final covered = workoutUnblockDomains.any(
        (domain) => domain == entry.key || domain.endsWith('.${entry.key}'),
      );
      if (covered) packages.addAll(entry.value);
    }
    return packages;
  }
}

Set<String> _stringSet(Object? value, String field) {
  if (value is! List) {
    throw PolicyFormatException('"$field" must be a list');
  }
  return value.map((e) => e! as String).toSet();
}

double _requireNum(Object? value, String field) {
  if (value is! num) {
    throw PolicyFormatException('"$field" must be a number');
  }
  return value.toDouble();
}

int _parseHhMm(Object? value, String field) {
  if (value is! String) {
    throw PolicyFormatException('"$field" must be a "HH:MM" string');
  }
  final parts = value.split(':');
  if (parts.length != 2) {
    throw PolicyFormatException('"$field" must be "HH:MM", got "$value"');
  }
  final hour = int.tryParse(parts[0]);
  final minute = int.tryParse(parts[1]);
  if (hour == null || minute == null || hour > 23 || minute > 59) {
    throw PolicyFormatException('"$field" is not a valid time: "$value"');
  }
  return hour * 60 + minute;
}